05-10-2018 07:17 AM - edited 03-08-2019 02:58 PM
Good Afternoon,
I have an SG550X 24 and an SG500 28 which are connected together in a two port LAG. The configurations are as follows:
SG550X:
interface TengigabitEthernet1/0/1 channel-group 1 mode auto switchport mode trunk ! interface TengigabitEthernet1/0/2 channel-group 1 mode auto switchport mode trunk ! interface Port-Channel1 spanning-tree link-type point-to-point switchport mode trunk switchport trunk native vlan 500 switchport trunk allowed vlan remove 1-69,72-4094 no macro auto smartport !
SG500
interface gigabitethernet1/25 channel-group 1 mode auto ! interface gigabitethernet1/26 channel-group 1 mode auto ! interface Port-channel1 spanning-tree link-type point-to-point switchport trunk allowed vlan add 70-71 switchport trunk native vlan 500 no macro auto smartport !
The issue is I am seeing "%CDP-W-NATIVE_VLAN_MISMATCH: Native VLAN mismatch detected on interface Po1" in the log on the SG550x constantly but not in the SG500.
CDP also reports that the native vlan on the member ports of the LAG from the SG500 is VLAN 1.
Platform: Cisco SG500-28 (PID:SG500-28-K9)-VSD Capabilities: Switch IGMP Interface: te1/0/1, Port ID (outgoing port): gi1/25 Holdtime: 120 Version: 1.4.8.6 Duplex: full Native VLAN: 1
Both switches are on the latest available firmware release. I have this configuration on port-channels from SG250's to both the SG550 and SG500 with no issues reported, it's purely between the SG550 and SG500.
I have noticed that if I ammend the allowed vlans on the SG550X to include VLAN 500 this appears to go away. I've never had issues excluding the native VLAN from the allowed list before by I usually work with Catalyst switches. It appears almost as if the SG550X doesn't want to allow the native VLAN to be excluded from the allowed list between it and the SG500.
Can anyone offer any advice on what might be causing this?
Thanks!
05-11-2018 01:34 PM
Hello!
Can you review if the device has the same native vlan in the physical ports?
Do not forget to rate useful post.
Regards,
05-11-2018 02:30 PM - edited 05-11-2018 02:31 PM
Hi,
Please try the following on SG500:
interface gigabitethernet1/25 channel-group 1 mode desirable
switchport mode trunk ! interface gigabitethernet1/26 channel-group 1 mode desirable
switchport mode trunk ! interface Port-channel1 spanning-tree link-type point-to-point
switchport mode trunk switchport trunk allowed vlan add 70-71 switchport trunk native vlan 500 no macro auto smartport !
HTH,
Meheretab
05-11-2018 02:59 PM
Hello,
what happens if you set the channel-group mode to 'on' instead of 'auto' ?
05-14-2018 02:11 AM
Thank you for replies everyone.
There appears to be significant differences between the trunk configuration and behaviour on the SG500 and SG550X. From your queries:
Switchport VLAN Settings:
SG500 cannot set the native vlan on the member ports of the LAG.
SG500(config)#int gi1/8 SG500(config-if)#switch trunk native vlan 500 Port gi1/8 belongs to a port-channel.
SG550X:
interface GigabitEthernet1/0/1 channel-group 2 mode auto switchport mode trunk switchport trunk native vlan 500 ! interface GigabitEthernet1/0/2 channel-group 2 mode auto switchport mode trunk switchport trunk native vlan 500 !
Port-Channel VLAN Settings:
When configuring the SG500 and specifying "switch trunk allowed vlan add x" it uses an inclusive method in the config.
interface Port-channel1 spanning-tree link-type point-to-point switchport trunk allowed vlan add 70-71 switchport trunk native vlan 500 no macro auto smartport
You cannot include the native VLAN in the allowed vlans on the SG500. If i used the command:
switch trunk allowed vlan add 500
Then the SG500 removes the "switch trunk native vlan 500" and changes the port-channel to native vlan 1.
On the SG550X the config uses an exclusion method for the allowed vlans in the config when creating.
interface Port-Channel2 spanning-tree link-type point-to-point switchport mode trunk switchport trunk native vlan 500 switchport trunk allowed vlan remove 1-69,72-499,501-4094 no macro auto smartport
SG550X has the opposite native VLAN behaviour, if the native vlan specified is not included in the allowed vlans then the VLAN interface will not come up with the port.
Channel-Group modes
Channel groups modes supported are only ON or AUTO on both SG500 and SG550X.
SG500(config)#int gi1/8 SG500(config-if)#channel-group 4 mode on Add port without LACP auto Add port with LACP
Mode on appears to exhibit the same behaviour, I am using auto as this enables LACP which is desirable to detect link issues and remove the channel member affected.
Working Config
To get this working I had to do the following:
Working config:
SG500:
interface gigabitethernet1/25 channel-group 1 mode auto ! interface gigabitethernet1/26 channel-group 1 mode auto ! interface Port-channel1 spanning-tree link-type point-to-point switchport trunk allowed vlan add 70-71 switchport trunk native vlan 500 no macro auto smartport
SG550X:
interface TengigabitEthernet1/0/1 channel-group 1 mode auto switchport mode trunk switchport trunk native vlan 500 ! interface TengigabitEthernet1/0/2 channel-group 1 mode auto switchport mode trunk switchport trunk native vlan 500 ! interface Port-Channel1 spanning-tree link-type point-to-point switchport mode trunk switchport trunk native vlan 500 switchport trunk allowed vlan remove 1-69,72-499,501-4094 no macro auto smartport
This just seems to be a very odd difference in behaviour, the SG500 behaves more as I would expect in not needing the native VLAN to be in the allowed vlans, but the SG550X behaves more as I would expect in mirroring the same trunk settings on the memeber interfaces.
I know the SMB switches don't behave in exactly the same way as the catalyst enterprise switches but this is just a bit bizarre.
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